The findings suggest that policies that improve our environment and strengthen social protection systems may have measurable benefits for brain health
The biological age of the brain can be altered by environmental, social and political conditions, an international study involving Irish researchers has found.
Using data from 18,701 individuals across 34 countries, the research shows that a combination of societal exposures can have effects on the brain larger than the sum of their parts, shaping brain-aging across both healthy individuals and those with neurodegenerative conditions.
The researchers quantified 73 different environmental factors measured at country level indicators spanning air pollution, climate variability, green space, water quality, socioeconomic inequality, and multiple indicators of political and democratic contexts.
When modeled jointly, these factors explained up to 15 times more variance in brain-aging than any single exposure alone. This finding highlights a key shift: environmental influences on brain health are cumulative and nonlinear, with interactions across domains amplifying their biological impact.
The research was carried out in conjunction with the Global Brain Health Institute (GBHI) at Trinity College Dublin and published in Nature Medicine.
“We aimed to test whether the combined, syndemic effects of environmental exposures better explain variability in brain aging across populations than individual exposures or single clinical diagnoses,” said the study’s lead investigator Agustín Ibáñez.
The study identifies found that social exposures like poverty, inequality, and lack of support can strongly affect how the brain ages. These pressures are linked to faster aging in brain areas responsible for thinking, emotions, and social behaviour.
The authors suggest that this may happen because the brain is constantly adapting to long-term stress. They argue that these combined social challenges can have an even bigger impact on brain aging than diseases like dementia and cognitive impairment.
Combined physical exposures such as increased pollution, extreme temperatures and a lack of green spaces, were primarily associated with structural brain aging, particularly affecting regions, central to memory, emotional regulation, and autonomic functions.
These structural changes are consistent with mechanisms such as neuroinflammation, oxidative stress, and vascular dysfunction, all of which may contribute to tissue degeneration.
For Agustina Legaz, first author of the study, Atlantic Fellow at GBHI and researcher at San Andres University, the work ‘provides a quantitative framework to understand how multiple environmental exposures jointly shape brain aging beyond individual determinants’.
The findings suggest that policies that reduce air pollution, expand access to urban green spaces, improve water quality, and strengthen social protection systems may have measurable benefits for brain health at the population level.
Read the study: The exposome of brain ageing across 35 countries – Nature Medicine.